Where are the o2 sensors on my x5?!!

Hey guys, I've got a 2001 X5 4.4i that I'm replacing all the O2 sensors in. I've done the two on the exhaust, But I CANNOT find the other two under the hood in the engine bay. Where EXACTLY are these stupid things located? It's driving me crazy. i've got all the tools and the sensors but i just can't find the sensor to replace it. Anybody have the foggiest?

Go upstream from the two you have replaced. They are located right behind the flange.

Good luck!

Found them. Thanks. I'm an idiot. Apparently we have these things called "eyes" and we're supposed to use them. Really easy job. Didn't use the slotted socket that I bought for $30!!!! dang it. A closed 22mm wrench reached in there perfectly and were able to pop them all out no problem. Thanks